1. Field of the Invention
The present invention relates generally to computer systems and specifically to the extension of video interface operational cable distance.
2. Description of the Related Art
The components of a computer system (such as PCs, minicomputers and mainframes) may be divided into two functional units, as illustrated in FIG. 1A—the computing system 102 and the human interface (or “HI”) to the computing system. For a PC, the computing system may be the CPU, memory, hard drive, power supply and similar components. The computing system may be comprised in a chassis which holds the motherboard, power supply, hard drive and the like. The human interface, on the other hand, may comprise those devices that humans use to transfer information to and/or receive information from the computing system. The most commonly recognized devices which form part of the human interface with the computing system include the monitor, keyboard, mouse and printer. The human interface may comprise a variety of other devices, such as a joystick, trackball, touchpad, microphone, speakers, and telephone, as well as other devices too numerous to specifically mention.
In current computer systems, e.g., current PC architectures, the human interface (e.g., the display monitor, mouse, and keyboard, etc.) is closely located to the computer system, by a distance typically less than about 10 feet. The computing system 102 generates and/or receives human interface signals, e.g., display monitor, mouse and keyboard formatted data, that are provided directly to/from the human interface 130 or desktop via individual specialized cables as illustrated in prior art FIG. 1A. For example, for most PCs installed at workstations, the computer monitor 116, keyboard 112 and mouse 114 rest on the desktop while the computer chassis which holds the computing system 102 rests on the floor underneath the desktop. Prior art FIG. 1B is a block diagram of the computer system illustrated in FIG. 1A. As indicated in FIG. 1B, the computing system 102 typically includes a processor 106, i.e., a CPU, a memory 104, and I/O interface logic, such as a video card 136 and an I/O interface card 137 which are coupled to the processor 106 through an I/O bus 124. The computing system 102 also typically includes chip set logic 108 for interfacing the processor 106 and memory 104 with the I/O bus 124. As is well known, two or more computing systems 102 may be connected together in a network configuration.
In order to fully resolve the aforementioned issues, in some current systems the entire computing system is physically separated from the human interface, specifically, by keeping the human interface (monitor, keyboard, mouse and printer) at the desktop or workstation while relocating the associated computing system (motherboard, power supply, memory, disk drives, etc.) to a secured computer room where plural computing systems are maintained. By securing the computing systems in one room, the employer's control over the computer systems is greatly enhanced. For example, since employees no longer have personal access, through the floppy or CD drive, to the memory subsystem, employees can not surreptitiously remove information from their computing system. Nor can the employee independently load software or other data files onto her computing system. Similarly, the employee can no longer physically change settings or otherwise modify the hardware portion of the computer. Maintenance is also greatly facilitated by placement of all of the computing systems in a common room. For example, the repair technicians and their equipment can be stationed in the same room with all of the computing systems. Thus, a technician could replace failed components or even swap out the entire unit without making repeated trips to the location of the malfunctioning machine. Such a room can be provided with special HVAC and power systems to ensure that the room is kept clean, cool and fully powered.
U.S. Pat. No. 6,012,101 titled “Computer Network Having Commonly Located Computer Systems”; U.S. Pat. No. 6,119,146 titled “Computer Network Having Multiple Remotely Located Human Interfaces Sharing a Common Computing System”; U.S. Pat. No. 6,038,616 titled “Computer System With Remotely Located Interface Where Signals are Encoded at the Computer System, Transferred Through a 4-wire Cable, and Decoded at the Interface” disclose systems where a plurality of computing systems are located at one location, and the human interfaces associated with these computing systems are remotely located at respective desktops.
FIG. 2 illustrates an exemplary prior art system where the human interface is remotely located from the computing system. The system of FIG. 2 includes a computing system, an upstream encoder, a communication medium, a downstream decoder, and the human interface devices. The downstream decoder and the human interface devices are located remotely from the upstream encoder and the computing system. This system employs a protocol wherein human interface signals generated by the computing system are encoded by the upstream encoder into a format which allows transmission over a lengthy distance to the remote location where the human interface devices are located. The encoded signals are then transmitted over the communication medium. The encoded human interface signals are received and decoded by the downstream decoder at the remote location, being converted back into the originally generated human interface signals for propagation to the human interface devices. Human interface signals generated by the human interface devices are similarly encoded by the downstream decoder, transmitted over the communication medium, decoded by the upstream encoder, and provided to the computing system. Thus, to date the separation of the computing system from the human interface has involved extension of the human interface signals, (monitor, mouse, keyboard, USB and other I/O signals), i.e., extensions of already existing I/O signals, that is, the human interface signals are generated by the computer (or human interface device), are changed or reformatted as needed for transmission to a distant or remote location, and then converted back to their original format.
As illustrated in FIG. 2, the remotely located human interface includes a monitor used to display information on the screen. While using monitors when the human interface is located near the computer system itself is commonplace, it may not be practical to do so when the human interface is located remotely from the computer system. The distance at which the computer video signals may be transferred is typically limited, as the computer video signals may suffer considerable line losses. Furthermore, the transfer of computer video signals over a significant distance may require dedicated video cabling with possible special cable considerations. For example, multiple coaxial cables may be required to transfer computer video signals from a computer system to a remote display. Due to the cost and bulkiness of coaxial cables, this may be a less than desirable solution. Furthermore, the cabling requirements for transferring computer video signals over a distance may leave no bandwidth for additional signals. Thus, any requirement for additional signals to be transferred to a remote location along with computer video signals may require additional cables beyond those already necessary. Such a solution may be both costly and logistically difficult to implement.
Certain prior art systems have operated to transfer analog R, G, B signals over twisted pair wiring at distances greater than 10 feet. However, improved methods are desired for transmitting analog video signal over a communication medium having distances greater than 10 feet.
Other corresponding issues related to the prior art will become apparent to one skilled in the art after comparing such prior art with the present invention as described herein.